The present invention relates to a wafer processing method and apparatus used for the fabrication of an integrated circuit (IC) semiconductor, more particularly, the present invention relates to a plasma processor and method having an improved processing rate and which is used for etching during IC fabrication.
Since the beginning of the IC industry, a wet etching method has been employed utilizing sulphuric acid, hydrochloric acid or phosphoric acid, however, recently the wet etching method has been replaced by a dry etching method, such as a plasma etching method. A plasma etching process has various advantages in comparison with the wet etching method, such as higher resolution, less undercutting, inherent cleanness, and a reduction in the number of fabricating processes, such as elimination of wafer rinsing and drying. Plasma etching, according to the present invention, in particular, makes it possible to perform sequential etching and stripping operations on the same machine, making it possible to realize fully automated IC fabrication.
A plasma is a highly ionized gas having a nearly equal number of positively and negatively charged particles and free radicals. The free radicals generated in plasma, act as a reactive species, chemically combine with materials to be etched, and form volatile compounds which are removed from the wafers by a vacuum.
During a process for forming fine patterns in the IC device, an etching process is performed, and in particular, the etching process includes both a true etching process and an "ashing" process which may be defined as a process for removing a photoresist mask which is usually an organic layer. The true etching process etches off the protective layers of silicon, silicon dioxide, etc. When ashing, oxygen (O.sub.2) is usually used as an etchant gas, and when etching a gas mixture of carbontetrafluoride (CF.sub.4) or carbon-tetrachloride (CCl.sub.4), etc. are used at a specified temperature and pressure.
Plasma processors can be classified into two types. In the first type a plasma is generated in a plasma generator and the activated plasma gas is introduced to the wafers in a separate location. In the second type, the wafers are placed in the plasma generating area. The first method is very slow and results in a wafer surface which is not uniform. The second method damages the wafer in the plasma environment due to bombardment by ions, ultraviolet rays, and soft X-rays, and, in addition, the wafer is contaminated with impurities from the plasma gas, resulting in widely varying quality of the wafer surfaces.